The invention relates to a small portable power converter adaptable to multiple battlefield operational modes for selection and use in accordance with various tactical needs as they arise in combat. One well-known need familiar to every combat soldier is to mask troop movements on the battlefield as well as conceal such critical combat items as tanks, artillery pieces, command posts, armored carriers, communication centers and other equipment common to ground warfare. Similarly, the Navy has a need to screen its warships at sea against observation or pinpoint targeting by enemy missiles or the like. The Air Force combat need is for screening entire airfields against attack by enemy projectiles, both to confuse enemy observers and to blind incoming missiles or the like to prevent destruction of its aircraft on the ground.
These massive screening requirements are extremely difficult to achieve using such devices as smoke-generators known to the prior art. The Army has not developed and fielded any new smoke-generators since the M3A3 was designed about 1958. The M3A3 weighs around 167 pounds and employs a pulse-jet engine to create and disperse smoke. Its use is limited to visual obscuration since it is not adaptable for use with anything other than hydrocarbon liquid oils used to create smoke. Solid particle agents which can blind enemy observation and target-seeking devices involving radar, infra-red or laser technology cannot be disseminated by the M3A3 smoke-generator. Also it is poorly adapted to screen the Army's newest tank, the M1 which travels faster than tanks of the past.
Another problem with prior smoke-generators is that turbines have not been used until very recently. When turbines or conventional auxiliary power turbines are used for smoke generation, they are very costly and need to be mounted on fixed or stationary platforms rather than on vehicles or other mobile units. This is because turbines generally are precision made devices characterized by very close tolerances and clearances between stationary and moving vanes. They are very sensitive to vibration due to their close tolerances and narrow clearances, hence must be shock-mounted even on a stationary base. Auxiliary power turbines used on aircraft are generally of low weight and have different vibration patterns, usually high frequency and low amplitude vibrations such as encountered in supersonic aircraft characterized by relatively straight trajectories or flight paths and an absence of bumps or sudden changes of direction. Ground vehicles have low frequency but high amplitude vibrations such as jeeps driving over bumpy or rough terrain. Aircraft turbines cannot survive the pounding which they would have to endure if mounted on a jeep, for example. Also, maintenance costs are very high with turbines, particularly due to high labor cost associated with expensive precision-made replacement parts and the use of turbine mechanics. Moreover, the size of aircraft turbines is an inverse function of the turbine speed squared. To double the rotational speed of a turbine, its size would have to be reduced to approximately 1/4 of its volume at the old speed. Aircraft turbines, which are very large, typically rotate between 55 and 60 thousand RPM. They are controlled by their rotating speed to a relatively narrow operating range. Although they are not well suited for disseminating smoke, some attempts have been made to adapt them for this purpose because of the large volume and relatively high velocity of exhaust gas associated with their operation. One model, presently under development, of a smoke-generator using a turbine of the foregoing type weighs 1400 pounds, requiring a 3/4 ton trailer to haul it and costs $70,000 without the trailer. Of this amount, $30,000 comprises equipment and components separate from the turbine which are necessary to operate it. Smoke generation is the only operational capability offered by this item, and it produces only one-third of the smoke generation rate achieved by the invention in this case costing about $5,000.
The Navy is interested in large smoke screening operations such as to obscure an entire aircraft carrier traveling in a 50 knot wind. This would represent 25 knots forward speed of the carrier plus a 25 knot headwind such as would be expected during flight operations when the carrier must sail directly into the wind in order to launch airplanes from its flight deck. Although flight operations must be interrupted when enemy incoming missiles are detected, Navy doctrine does not permit radical direction changes from the headwind orientation. This requires a massive smoke output for screening purposes. The Navy has an additional problem due to the particular vulnerability of turbines to salt, even atmospheric salt common to the open sea which are ingested into the turbines. Turbines suffer rapid structural deterioration and breakdown from any contact with salt in any amount during turbine operation characterized by high temperatures. Due to this particular susceptibility for rapid and precipitous damage, expensive alloys and surface treatments are necessary to enable a turbine for use at sea to withstand salt corrosion. Such turbines are said to be "marinized" for Navy use. An aircraft turbine, if marinized for example, costs $200,000 more than the same turbine not marinized.
In addition to the foregoing deficiencies, smoke-generators known to the prior art typically require long start up times and complex procedures for starting such as manually priming the energy source, hand cranking of the turbine to bring it up to sufficient rotational speed and continuous control to balance essential starting parameters by the operator. Such control may involve several different inputs to compensate for speed, fuel, air supply and feeding rate of smoke agents. Moreover, the massive bulk and weight of such units and their sensitivity to vibration and other factors limit their use to slow moving or stationary bases. In addition, such units lack versatility in that they are limited to one particular operational use or purpose, namely, generating smoke. Where the enemy battlefield threat consists of infra-red and laser aiming or target acquisition devices, it is necessary to use entirely different materials to screen tanks, grounded aircraft or Navy vessels. When a combat vehicle is moving at high speed over land surfaces or through the water, the screening source is required to move in advance of the screened object to maintain adequate coverage thereof. Prior art smoke-generators cannot be vehicle mounted and move as rapidly over terrain as the M-1 tank travels. This is because they cannot withstand jolting and because the smoke output of such devices is so limited that it will not generate a sufficiently heavy screen when traveling at high speed to obscure the M-1 tank which is quite large and not easily camouflaged.